Air heating system for power generators



y 3, 1955 J, H. BAYARD 2,707,457 AIR HEATING SYSTEM FOR POWER GENERATORSFiled April 22, 1950 Fit 0 W67 INVENTOR.

United States Patent AIR HEATING SYSTEM FOR POWER GENERATORS Julius H.Bayard, Charleston, S. C., assignor to Foster Wheeler Corporation, NewYork, N. Y., a corporation of New York Application April 22, 1950,Serial No. 157,544 6 Claims. (Cl. 122-1) This invention relates to heatexchange apparatus and more particularly to a preheater system for avapor generator.

It is usual in vapor generators to heat feed water therefor in aneconomizer positioned in heat exchange relationship with gases from thefurnace of the vapor generator which, in turn, lowers the temperature ofsaid gases. If the temperature of the feed water entering the economizeris of such degree that the heat removed from the gases does not lowerthe gas temperature to the desired degree an air heater is positioned inheat exchange relationship with gases beyond the economizer in thedirection of flow of the gaes. Since the specific heat of the exhaustgases in relationship to the air is low, the size of the air heater isnormally very large.

In accordance with the present invention, a portion of the feed water,all of which water is normally preheated to a degree less than thedesired final temperature in a feed water heater by indirect heattransfer from steam, for example from the exhaust steam of a turbine, ispassed in indirect heat exchange relationship with air to be used tosupport combustion in the furnace of a vapor generator, or for otheruses. The portion of the feed water passing in heat exchangerelationship with the air is cooled as the air is heated. After coolingin the air heater, said one portion of the feed water is passed to theinlet of one section of an economizer which economizer comprises twosections, said one section of the economizer being located beyond theother section of the economizer in the direction of flow of combustiongases from the furnace so that said gases pass in heat exchangerelationship with said other section prior to passing in heat exchangerelationship with the one section. In flowing through said one sectionof the economizer, the one portion of the feed water is reheated andregains a part or all of the heat given up to the air flowing throughthe air heater. Since said one portion of the feed water is relativelycool when it enters the one sec tion of the economizer, the gastemperature of the combustion gases from the furnace is greatly reducedas it passes in heat exchange relationship with said one section of theeconomizer. After flowing through the one section of the economizer,said one portion of the feed water is passed into the other section ofthe economizer together with the other portion of the feed water passingfrom the feed water heater. Both portions of the feed water then flowthrough said other section of the econornizer and thence into the vaporgenerator. A proportioning control valve is provided for controlling theportion of the feed water flowing to the air heater and the portionflowing directly to said other section of the e'conomizer.

The present invention provides apparatus for preheating feed water andpreheating air for a vapor generator in which the temperature of theflue gases of a vapor generator may be controlled and in which expansiontanks and the like are not necessary.

This invention also provides apparatus for preheating 2,707,457 PatentedMay 3, 1955 air and feed water for a vapor generator in which separatefeed water pumps are not required and in which the possibility of airheater fires are greatly reduced and in which the air heater may bepositioned in any desired location.

The invention will be understood from the following description whenconsidered in connection with the accompanying drawing forming a partthereof and in which the single figure is a somewhat diagrammatictransverse vertical section of the apparatus of the present invention.

Referring to the drawings, the apparatus of the pres ent invention isdisclosed as embodied in a vapor generator comprising a setting 10having vapor generating surface therein with an upper steam and waterdrum 11 associated therewith together with a lower water drum 12 in thelower part of the setting in substantial vertical alignment with saidupper drum. Drums 1]. and 12 are connected by a substantially verticalbank of steam generating tubes 13 having a central battle 14 extendingfrom said lower drum upwardly to a point short of the upper drum. At oneside of the bank of tubes 13 is a furnace or combustion chamber 15fired, as shown, by a plurality of burners 16. The root and side wall ofchamber 15 is lined by water tubes 17. At the opposite side of bank 13is a gas outlet passage 18 which communicates with gas inlet 19 of flueor stack 20. The flue has a gas outlet 21 which acts as a gas outlet forthe setting.

An economizer 22 having an upper or one section 23 with a feed waterinlet 24 and a feed water outlet 25 is positioned in flue 20. Economizer22 has a lower or other section 26 over which gases from gas passage 18pass prior to flowing in heat exchange relationship with upper section23. Lower section 26 of the economizer has a feed water inlet 27 and afeed water outlet 28. Feed water outlet 28 is in communication with thewater space of drum 11 through a conduit 29.

As shown, feed water to be used in the vapor generator, which feed watermay be condensate from a con-' denser, not illustrated, enters a feedwater preheater 30 through a feed conduit 31 and fiows through aplurality of tubular members 32 in said heater. The water flowingthrough tubular members 32 is heated by steam, for example steamexhausted from a turbine, not shown, which steam enters the feed waterpreheater through steam in let 33 and passes therefrom through outlet 34after flowing in heat exchange relationship with tubular members 32.Feed water heated by flowing through tubular members 32 passes from thepreheater through an outlet conduit 35 and into the inlet of feed liquidflow controlling means which, as shown, is a proportioning control valveillustrated diagrammatically at 36. Control valve 36 has a proportioningvalve member 37 which is operable to proportion the feed water betweenan economizer feed line 38 and an air heater feed line 39. Economizerfeed line 38is in communication at one end thereof with one outlet ofvalve 36 and at the opposite end with inlet 27 of economizer section 26,while air heater feed line 39 is in communication at one end thereofwith another outlet of valve 36 and at the opposite end with inlet 40 ofan air heater 41.

Air heater 41 comprises a plurality of tubes 42 extend ing transverselyof air conducting means or air conduit 43. Adjacent tubes are connectedby return bends 44 and 45 so that feed water entering the air heaterthrough inlet 40 passes in a continuous path of flow from the lower tubeto the upper tube thereafter to pass from the air heater at outlet 46.As shown, tubes 42 have extended surface members 47 thereon. Air conduit43 is in communication above air heater 41 with a source of air to beheated and extends below said air heater and into communication with thefurnace 15 through burners 16.

Feed Water which has passed through air heater 41 flows therefromthrough outlet 46 and into the one section 23 of economizer 22 throughconduit 43 which communicates at one end with outlet 46 and at theopposite end with inlet 24- of economizer section 23. Feed water whichenters section 23 of economizer 22 through inlet 24 flows therethroughand thence into section 26 through outlet 25, conduit 49 and economizerfeed line 38.

In operation, gases of combustion from combustion chamber 1.5 flowtherefrom into bank of tubes 13 and are directed upwardly by baflie 14over some of the tubes thence downwardly over the remainder of the tubesand into gas passage 18. From gas passage 18, the gases flow throughoutlet 19 thence in heat exchange relationship with the tubes ofeconomizer section 26 and thereafter in heat exchange relationship withthe tubes of economizer section 23.

Feed water to be heated for the vapor generator passes into feed waterpreheater 30 through feed conduit 31 and is heated therein thereafter topass therefrom into outlet conduit 35. Proportioning control valve 36 isset so that a desired portion of the heated feed water passes directlyto economizer portion 26 and another desired proportion of the heatedwater flows to air heater 41.

By controlling the proportion of feed water passing through air heaterfeed line 39 and through air heater 41 to economizer section 2.3 throughconduit 48, the temperature of the flue gases passing through outlet 21may be controlled. The feed water passing through air heater 41 iscooled considerably by the air flowing through conduit 43, said waterentering economizer section 23 at a relatively low temperature. Forexample, the temperature of the feed water passing into proportioningcontrol valve 36 would be approximately 390 F. and would pass througheconomizer feed line 38 thereafter to enter economizer section 26 atapproximately that temperature. The proportion of the feed water flowingthrough valve36 into air heater 41 would enter the air heater atapproximately 390 F. and would be cooled in the air heater toapproximately 180 F. at outlet 46 by air which enters conduit 43 atabout 100 F. and after flowing in heat exchange re lationship with tubes42 of air heater 41 enters the furnace or combustion chamber 15 throughburners 16 at substantially 340 F. The feed water entering section 23through conduit 48 would therefore be at approximately 180 F. Exhaustgases entering flue gas inlet 19 of the flue 20 would be, for example,600 F. and first flow over economizer section 26 and thereafter overeconomizer section 23 thereby becoming cooled to approximately 320 F. atflue outlet 21. 23 would be passed into conduit 38 at substantially 390P. which would be approximately equal to the temperature of theproportion of the feed water flowing from valve 36 through economizerfeed line 38 to economizer Feed water flowing through section section26. All of the feed water entering economizer section 26 would,therefore, be at substantially 390 F. and would be heated toapproximately 460 F. at outlet 28 of economizer section 26.

Inasmuch as changes may be made in the form, location and relativearrangement of the several parts of the apparatus disclosed withoutdeparting from the essential characteristics of the invention, it willbe understood that the invention is not to be limited excepting by thescope of the appended claims.

What is claimed is:

1. In vapor generating apparatus comprising a vapor generator having asetting, a furnace in the setting, means for firing the furnace, saidsetting having a gas outlet in communication with the furnace andthrough which gases of combustion flow from the setting, vaporgenerating surface in the setting in heat exchange relationship withsaid gases of combustion prior to the flow of said gases from thesetting gas outlet, aneconomizer for heating liquid for said vaporgenerating surface, the economizer being positioned in heat exchangerelationship withgases of com bustion flowing from the setting afterpassing in heat exchange relationship with said vapor generatingsurface, the economizer having a plurality of sections, one sectionthereof being positioned beyond another section in respect to the flowof said gases to the setting gas outlet, said economizer sections eachhaving an inlet through which liquid enters the section and an outletthrough which liquid passes from the section after flow therein, theoutlet of said one economizer section being in communication with theinlet of said other economizer section, conduit means communicating withthe outlet of said other economizer section and the vapor generatingsurface, an air heater comprising air conducting means through which airto be heated flows and a tubular path of flow having a liquid inict anda liquid outlet, the liquid outlet being in communication with the inletof said one economizer section, said tubular path of flow being disposedin heat exchange relationship with air passing through said airconducting means, a feed liquid preheater having a feed liquid inletthrough which feed liquid to be heated enters the heater and a feedliquid outlet through which heated feed liquid flows from the heater, aneconomizer feed liquid conduit in communication with the inlet of saidother economizer section and with said preheater outlet, an air heaterfeed liquid conduit in communication with the inlet of the air heatertubular path of flow and with said preheater outlet, and control meansfor controlling the flow of heated feed liquid from said preheater tothe air heater tubular flow path and from said preheater to said othereconomizer section.

2. In vapor generating apparatus comprising a vapor generator having asetting, a furnace in the setting, means for firing the furnace, saidsetting having a gas outlet in communicating with the furnace andthrough which gases of combustion flow from the setting, vaporgenerating surface in the setting in heat exchange relationship withsaid gases of combustion prior to the flow of said gases from thesetting gasoutlet, an economizer for heating liquid for said vaporgenerating surface, the economizer being positioned in heat exchangerelationship with gases of combustion flowing from the setting afterpassing'in heat exchange relationship with said vapor generatingsurface, the economizer having a plurality of sections, one

section thereof being positioned beyond another section in respect tothe flow of said gases to the setting gas outlet,

said economizer sections each having an inlet through which liquidenters the section and an outlet through which liquid passes from thesection after flow therein, the outlet of said one economizer sectionbeing in communication with the inlet of said other economizer section,conduit means communicating with the'outlet of said other economizersection and the vapor generating surface, an air heater comprising airconducting means through which air to be heated flows and a tubular pathof flow having a liquid inlet and a liquid outlet, the liquid outletbeing in communication with the inlet of said one economizer section,said tubular path of flow being disposed in heat exchange relationshipwith air passing through said air conducting means, a feed liquidpreheater having a feed liquid inlet through which feed liquid to beheated enters the heater and a feed liquid outlet through which heatedfeed liquid flows from the heater, an economizer feed liquid conduit incommunication with the inlet of said other economizer section and withsaid preheater outlet, an air heater feed liquid conduit incommunication with the inlet of the air heater tubular path of flow andwith said preheater outlet, and a liquid proportioning control valve sodisposed in relationship to said preheater outlet as to control theproportionof heated feed liquid flowing from said preheater to the airheater tubular flow path inlet and to the inlet of said other economizersection.

3. In vapor generating apparatus comprising a vapor generator having asetting, a furnace in the setting, means for firing the furnace, saidsetting having a gas outlet in 6 communication with the furnace andthrough which gases of combustion flow from the setting, vaporgenerating surface in the setting in heat exchange relationship withsaid gases of combustion prior to the flow of said gases from thesetting gas outlet, an economizer for heating liquid for said vaporgenerating surface, the economizer being positioned in heat exchangerelationship with gases of combustion flowing from the setting afterpassing in heat exchange relationship with said vapor generatingsurface, the economizer having a plurality of sections, one sectionthereof being positioned beyond another section in respect to the fiowof said gases to the setting gas outlet, said economizer sections eachhaving an inlet through which liquid enters the section and an outletthrough which liquid passes from the section after flow therein, theoutlet of said one economizer section being in communication with theinlet of said other economizer section, conduit means communicating withthe outlet of said other economizer section and the vapor generatingsurface, an air heater comprising air conducting means through which airto be heated flows and a tubular path of flow having a liquid inlet anda liquid outlet, the liquid outlet being in communication with the inletof said one economizer section, said tubular path of flow being disposedin heat exchange relationship with air passing through said airconducting means, a source of heated feed liquid, an economizer feedliquid conduit in communication with the inlet of said other economizersection and with said source, an air heater feed liquid conduit incommunication with the inlet of said air heater tubular path of flow,and control means for controlling the flow of preheated feed liquid fromsaid source to the air heater tubular flow path and from said source tothe other economizer section.

4. In vapor generating apparatus comprising a vapor generator having asetting and a saturated vapor space, a furnace in the setting, means forfiring the furnace, gas passage forming means in communication with thefurnace to receive gases of combustion therefrom, an

economizer in said passage in heat exchange relationship 1 with gasesflowing therethrough, the economizer having a plurality of sections, oneof said sections being positioned beyond another section in thedirection of flow of gases through the passage, the outlet of said oneeconomizer section being in communication with the inlet of said othereconomizer section, the outlet of said other economizer sectioncommunicating with said vapor generator, an air duct in communicationwith said furnace to conduct heated air thereto, tubular means arrangedto form a tubular path of flow and disposed in heat exchangereiationship with said air flowing to the furnace, the outlet of saidtubular path of flow being in communication with the inlet of said oneeconomizer section, means for preheating feed liquid, saidlast-mentioned means being in communication with the inlet of said othereconomizer section so as to deliver heated feed liquid thereto, saidinlet of the tubular flow path also being in communication with thepreheated feed liquid means to receive heated feed liquid therefrom, andcontrol means constructed and arranged to control the flow of preheatedfeed liquid from the preheated feed liquid means to said tubular flowpath and also to the other economizer section.

5. The apparatus of claim 4 wherein the control means comprises amovable liquid proportioning control valve so disposed in relationshipto said preheated feed liquid means as to control the proportion ofpreheated feed liquid flowing therefrom to the tubular flow path and toother economizer section said valve being movable in one direction toincrease the flow of liquid to the tubular flow path while decreasingthe flow to said other economizer section and movable in anotherdirection to decrease the flow of liquid to the tubular flow path whileincreasing the iiow to said other economizer section.

6. in vapor generating apparatus comprising a vapor generator having asetting and a saturated vapor space, a furnace in the setting, means forfiring the furnace, gas passage forming means in communication with thefurnace to receive gases of combustion therefrom, an economizer forheating liquid for said vapor generator, the economizer being positionedin heat exchange relationship with gases of combustion flowing from thesetting after passing in heat exchange relationship with said vaporgenerator and comprising a plurality of sections, the outlet of oneeconomizer section being in communication with the inlet of the othereconomizer section, the outlet of said other economizer sectioncommunicating with said vapor generator, an air duct in communicationwith said furnace to conduct heated air thereto, tubular means arrangedto form a tubular path of flow and disposed in heat exchangerelationship with said air flowing to the furnace, the outlet of saidtubular path of flow being in communication with the inlet of said oneeconomizer section, means for preheating feed liquid, saidlastincntioned means being in communication with the inlet of said othereconomizer section so as to deliver heated feed liquid thereto, saidinlet of the tubular flow path also being in communication with thepreheated feed liquid means to receive heated feed liquid therefrom, andcontrol means constructed and arranged to control the flow of preheatedfeed liquid from the preheated feed liquid means to said tubular flowpath and also to the other economizer section.

References Cited in the file of this patent UNITED STATES PATENTS1,235,928 Sargent et a1 Aug. 7, 1917 1,285,201 iacobus et al. Nov. 19,1918 1,753,363 Coghlan et al. Apr. 8, 1930 1,833,130 Roe Nov. 24, 19311,975,519 Rudorff Oct. 2, 1934

1. IN VAPOR GENERATING APPARATUS COMPRISING A VAPOR GENERATOR HAVING ASETTING, A FURNACE IN THE SETTING, MEANS FOR FIRING THE FURNACE, SAIDSETTING HAVING A GAS OUTLET IN COMMUNICATION WITH THE FURNACE ANDTHROUGH WHICH GASES OF COMBUSTION FLOW FROM THE SETTING, VAPORGENERATING SURFACE IN THE SETTING IN HEAT EXCHANGE RELATIONSHIP WITHSAID GASES OF COMBUSTION PRIOR TO THE FLOW OF SAID GASES FROM THESETTING GAS OUTLET, AN ECONOMIZER FOR HEATING LIQUID FOR SAID VAPORGENERATING SURFACE, THE ECONOMIZER BEING POSITIONED IN HEAT EXCHANGERELATIONSHIP WITH GASES OF COMBUSTION FLOWING FROM THE SETTING AFTERPASSING IN HEAT EXCHANGE RELATIONSHIP WITH SAID VAPOR GENERATINGSURFACE, THE ECONOMIZER HAVING A PLURALITY OF SECTIONS, ONE SECTIONTHEREOF BEING POSITIONED BEYOND ANOTHER SECTION IN RESPECT OMIZERSECTIONS EACH HAVING AN INLET THROUGH WHICH LIQUID ENTERS THE SECTIONAND AN OUTLET THROUGH WHICH LIQUID PASSES FROM THE SECTION AFTER FLOWTHEREIN, THE OUTLET OF SAID ONE ECONOMIZER SECTION BEING INCOMMUNICATION WITH THE INLET OF SAID OTHER ECONOMIZER SECTION, CONDUITMEANS COMMUNICATING WITH THE OUTLET OF SAID OTHER ECONOMIZER SECTION ANDTHE VAPOR GENERATING SURFACE, AN AIR HEATER COMPRISING AIR CONDUCTINGMEANS THROUGH WHICH AIR TO BE HEATED FLOWS AND A TUBULAR PATH OF FLOWHAVING A LIQUID INLET AND A LIQUID OUTLET, THE LIQUID OUTLET BEING INCOMMUNICATION WITH THE INLET OF SAID ONE ECONOMIZER SECTION, SAIDTUBULAR PATH OF FLOW BEING DISPOSED IN HEAT EXCHANGE RELATIONSHIP WITHAIR PASSING THROUGH SAID AIR CONDUCTING MEANS, A FEED LIQUID PREHEATERHAVING A FEED LIQUID INLET THROUGH WHICH FEED LIQUID TO BE HEATED ENTERSTHE HEATER AND A FEED LIQUID OUTLET THROUGH WHICH HEATED FEED LIQUIDFLOWS FROM THE HEATER, AN ECONOMIZER FEED LIQUID CONDUIT INCOMMUNICATION WITH THE INLET OF SAID OTHER ECONOMIZER SECTION AND WITHSAID PREHEATER OUTLET, AN AIR HEATER FEED LIQUID CONDUIT INCOMMUNICATION WITH THE INLET OF THE AIR HEATER TUBULAR PATH FO FLOW ANDWITH SAID PREHEATER OUTLET, AND CONTROL MEANS FOR CONTROLLING THE FLOWOF HEATED FEED LIQUID FROM SAID PREHEATER TO THE AIR HEATER TUBULAR FLOWPATH AND FROM SAID PREHEATER TO SAID OTHER ECONOMIZER SECTION.